Electronic devices integrated in a tire can provide functions such as identification and tracking during manufacture, distribution, and use, and measurement of physical parameters such as pressure and temperature during use of the tire. Many systems utilize radio frequency communication between the tire and the external monitoring or interrogating device. A radio frequency communication link requires one or more antennas.
An electronic device and antenna that is securely attached to a tire structure, for example, by being embedded in the elastomeric material of the tire or attached by means of an elastomeric patch that is bonded to the tire, is desirable. Such mounting or attachment provides permanent, tamper-proof integration of the device with the tire. Integrating an antenna in the tire, however, presents difficulties. A tire undergoes flexing and distortions during normal use that can cause the antenna to fracture or separate from the electronics device. Further, if the electronics device and antenna are to be integrated with the tire during manufacture and before curing of the tire, the manufacturing process includes many steps, such as shaping and curing, which could cause the wire to break.
The invention provides an improved electronics device with a radio frequency antenna for integration with a tire that avoids problems in the art. According to the invention, the improved electronics device includes an antenna that is shaped to absorb stresses imposed on it by the tire or tire manufacturing process. According to the invention, the antenna is shaped as a spiral winding, which provides extensibility in the longitudinal direction and flexibility in other directions. According to a preferred embodiment, the antenna has a helical shape, having a plurality of turns along its length.
An improved electronic communication device for a tire of a vehicle, according to the invention, comprises a radio device for communicating information from the tire to a remote radio receiver, and at least a first antenna wire connected to and extending from said radio device, the at least first antenna wire is formed with a plurality of helical turns, characterised in that the antenna is completely coated with an electrically insulating material.
Preferably, the radio device is also coated with an electrically insulating material.
According to one embodiment of the invention, the antenna wire is formed as a monopole or dipole antenna and terminates at a distance from the radio device. This embodiment is useful for relatively high frequency radio devices, for example, the radio devices operable at a frequency at or above 130 MHz.
According to another embodiment, the antenna wire forms a loop antenna, which is advantageous for lower frequency communication. Such devices may operate, for example, at about 13 MHz, or less.
The antenna material can be any material capable of transmitting radio frequency energy. Advantageously, and preferably for use in or on a tire because of its durability under fatigue conditions, the antenna body is a wire formed of spring steel, brass coated spring steel, spring brass or some copper alloys and coated steel. Such materials are capable of surviving the bending and flexing deformations typically experienced by the tire.
According to another aspect of the invention, the device includes a rubber layer to facilitate integration of the device with a tire. Preferably, the layer of rubber material is electrically non-conductive and surrounds the radio device and the at least first antenna wire. The device may be integrated by embedding it in a portion of a tire, or by attaching to a surface of the tire in the manner of a patch.
The invention also includes a tire having an electronic communication device, the tire comprising a crown region and sidewalls extending radially inward from the crown and terminating in beads, the tire further comprising a radio device for communicating information from the tire to a remote radio receiver and at least a first antenna wire connected to and extending from said radio device, the antenna being formed with a plurality of helical turns, the invention characterised in that the radio device and antenna are integrated into the tire with a coating of electrically non-conductive material surrounding the at least first antenna wire.
The radio device and antenna can be integrated in the sidewall of the tire. They can also be integrated in the crown of the tire.
The invention will be better understood by reference to the following detailed description in conjunction with the appended drawings.